Which motor is totally enclosed and not equipped for cooling by means external to the enclosing parts?

• A. Totally Enclosed Motor
• B. Totally Enclosed Nonventilated Motor
• C. Totally Enclosed Fan-Cooled Motor
• D. Open Motor

Answer: (B)

Totally enclosed nonventilated describes a motor that is sealed so there are no openings for outside air to enter or leave, and it has no external cooling paths such as vents, ducts, or a cooling fan drawing in ambient air. Cooling, if needed, must occur inside the enclosure and be conducted away through the enclosure walls. Because there’s no provision for external air cooling, this motor is not equipped to be cooled by means external to the enclosing parts, which is exactly what the question is asking.

The other descriptions don’t fit that requirement. A simply totally enclosed motor doesn’t specify whether it relies on internal air movement or external cooling paths. A totally enclosed fan-cooled motor uses a built-in fan to move air, which is an external cooling method relative to the windings but still largely relies on internal air flow within the enclosure. An open motor has openings to the outside and relies on ambient air for cooling, which clearly isn’t totally enclosed.